The HSDPA (High Speed Downlink Packet Access) method used in the WCDMA (Wideband Code Division Multiple Access) communication system is a method that effectively uses wireless resources by allowing a plurality of mobile station terminals to share one physical channel (HS-PDSCH: High Speed Physical Downlink Shared Channel).
In the HSDPA method, hexadecimal QAM (Quadrature Amplitude Modulation) or QPSK (Quadrature Phase Shift Keying) is adaptively applied as a wireless interval modulation method in accordance with the wireless propagation environment. High-speed downlink data transmission is achieved by performing multi-code transmission using a maximum of 15 codes. Also, the HSDPA method is characterized by adopting high-speed retransmission control performed between a base station apparatus and mobile station terminal by the HARQ (Hybrid Automatic Repeat Request) method.
In the HSDPA method, high-speed retransmission control is performed between a base station apparatus and mobile station terminal by the HARQ method. Therefore, data can be correctly transferred by retransmission control whose speed is higher than that of retransmission control performed by packet data transfer of the conventional WCDMA system by RLC (Radio Link Control) or TCP (Transmission Control Protocol) as an upper layer. That is, in the HSDPA method, retransmission control conventionally performed by an upper layer is reduced, and high-speed retransmission control is performed by the HARQ method, thereby preventing the decrease (data transfer delay) in throughput caused by retransmission.